0724-B3
L.M. Humble, E.A. Allen, E. Hurley, J.H Sun, C.Q. Gao and B.D. Gill 1
Numerous exotic bark and wood-boring beetles have recently been "discovered" around the world, usually well after their initial introduction. Each incursion has served to highlight the same question: How can effective surveillance for adventive bark and wood borers be undertaken? National and international surveillance projects are reviewed, research priorities are summarized, and possible approaches identified.
Surveillance programs for the detection of invasive species are an ongoing activity of agencies responsible for the detection of quarantine pests as well as those agencies managing forest resources. Such programs are intended to provide early detection of new incursions of exotic pests in sufficient time to develop eradication programs for preventing their permanent establishment, or to provide data on the geographic range of established non-indigenous species in support of regulatory controls or management programs. National systems of surveillance are required by the International Plant Protection Convention (Article IV2b) (FAO 1999) and are integral to International Standards for Phytosanitary Measures (e.g., FAO 1997). Knowledge of the distribution and impacts of invasive species are also included in international agreements such as:
During the past decade, many of the invasive species that have established in forest ecosystems have been associated with the global trade in wood and wood products. These invasive species present new and significant challenges for pest-surveillance programs. We will review the recent history of these pest incursions and discuss the challenges they present to the development and implementation of surveillance systems.
Over the past few decades, a significant number of non-indigenous bark and wood-boring beetles have been discovered in forests around the world. Since 1989, at least 23 species of bark or wood-boring beetles and wood wasps [Coleoptera: Scolytidae (15 spp.), Buprestidae (2 spp.), Cerambycidae (4 spp.), and Micromalthidae (1 spp.); Hymenoptera: Xiphydriidae (1 spp.)] have been discovered in forested habitats within North America (Atkinson et al. 1990, 1991; Bright and Rabaglia 1999; Cavey et al. 1998; Haack 2001; Haack and Kucera 1993; Haack et al. 2002; Hoebeke 1989, 1991, 1999, 2001; Humble 2001; Mudge et al. 2001; Rabaglia and Cavey 1994; Smith and Hurley 2000; Vandenberg et al. 2000).
Numerous interceptions and incursions of invasive species associated with wood products have also occurred in Europe. Krehan and Holschulz (2001) and Colombo and Limonta (2001) report incursions of two species of Anoplohora (Cerambycidae) in Austria and Italy respectively, while Holzschuh (1990) and Krehan and Holschulz (1999a) discovered an Asian ambrosia beetle in central Europe. Additional establishments of Cerambycidae in Europe are reported by Campadelli and Sama (1989) and Ruiz and Barranco (1998). Interceptions of eight species of wood borers (Coleoptera: Cerambycidae, Buprestidae; Hymenoptera: Siricidae) with imported sawlogs (Krehan and Holzschuh 1999b) indicate that further incursions are likely to be discovered in Europe.
Ciesla (1992) reported the presence of two North American species in imported logs in Anhui Province, China. More recently, a second North American species, the red turpentine beetle, has established in China (Yin 2000). Since its first outbreak in 1999, red turpentine beetle has spread rapidly from Shanxi Province to three other adjacent provinces (Hebei, Henan, and Shaanxi), infesting over half a million hectares of pine stands (Li et al. 2001; Miao et al. 2001).
The first line of defense against introductions of non-indigenous species is the inspection of imports by National Plant Protection Organizations such as the Canadian Food Inspection Agency (CFIA) or the U.S. Department of Agriculture's Animal and Plant Health Inspection Service. National Plant Protection Organizations are tasked with the responsibility of inspecting imported goods for the presence of harmful non-indigenous species. During these inspections, staff detect known pests that contaminate commodities, shipping containers, and packing materials. The volume of trade prevents the inspection of all imports, thus less than 2% of all imported commodities are inspected in the United States (National Research Council 2002) and Canada.
Records of intercepted species are maintained (e.g., see CFIA 2002a). Analysis of such records provides insight into the organisms inadvertently transported with commodities. From 1997 to 2000, 54% of the 1667 arthropod interceptions in Canada were from wood or wood products, with almost half (46%) consisting of bark and wood-boring beetles (Coleoptera: Anobiidae, Buprestidae, Cerambycidae, Lyctidae, Platypodidae, and Scolytidae) and wood wasps (Hymenoptera: Siricidae).
Pest-interception databases quantify the frequency with which pests of quarantine significance arrive in association with imports. However, the databases provide no information about the abundance of the individuals, because each record documents only species occurrence. The Canadian Forest Service, in collaboration with the Canadian Food Inspection Agency, has evaluated the abundance of pests in wood and wood packaging intercepted at western Canadian ports to quantify pest loads and to provide definitive identification of the adventive species.
Quantification of exotic species abundance arriving with trade provides data that are important to the evaluation of quarantine risk posed by individual species. The number of individuals initially introduced is a significant determinant of the likelihood of establishment of exotic species-larger populations increase the risk of establishment. Allen and Humble (2002) recovered more than 2500 adult insects representing more than 40 species of wood borers and their associates, including large numbers of four species of quarantine significance (Pityogenes chalcographus (L.), Polygraphus poligraphus (L.), Ips typographus (L.), and Tetropium fuscum (Fabricius)) from a single commodity shipment. Similar studies of infested wire-rope spools from China demonstrated the presence of six species of longhorned wood borers.
A significant consequence of the increased use of containerization in international trade has been the rapid and long-distance movement of sealed containers from the immediate port facilities to warehouses in urban areas. Forested habitats (parks and ornamental plantings) near urban importing facilities provide opportunities for invasive species to successfully establish (Humble and Allen 2001). It is not surprising that exotic species such as Anoplohora glabripennis (Motschulsky), Tetropium fuscum, and Agrilus planipennis Fairmaire were first discovered in heavily urbanized areas (Cavey et al. 1998; Smith and Hurley 2000; Haack et al. 2002). Therefore, during the past decade, surveillance for invasive forest pests has expanded beyond the immediate port facilities to encompass adjacent forest habitats.
In both Canada and the United States, these surveillance programs use Lindgren multiple funnel traps baited with commercially available attractants for wood borers (e.g., see Humble 2001; Mudge et al. 2001; CFIA 2002b) and specifically target frequently intercepted bark beetle species of high quarantine significance. To date the studies have demonstrated the establishment of some target species (Mudge et al. 2001; Haack 2001; Hoebeke 2001; Rabaglia and Cavey 1994) as well as at least nine other species of Scolytidae and one wood wasp exotic to North America. In addition, they have demonstrated the transfer of at least five native North American species of bark and ambrosia beetles to regions beyond their natural range (Humble 2001; Mudge et al. 2001; Rabaglia and Williams 2002).
With the exception of species for which pheromone-based lures are available (I. typographus and Trypodendron domesticum (L.)), lure systems employed against exotic Scolytidae, Cerambycidae, and Buprestidae discovered in North America during the last decade are relatively non-specific host volatiles. Unlike pheromone-based trap systems used for monitoring species such as gypsy moth, which are effective over relatively long distances, the monitoring systems employed in port surveillance have a limited range of effectiveness, generally less than 50 m.2
Significant challenges remain in the development of more effective surveillance tools for invasive bark and wood-boring beetles. Canadian Forest Service scientists are participating in the development of new trap designs and kairomone-based lures for the detection of T. fuscum, and in the development of more effective lures for the pine shoot beetle, Tomicus piniperda, in North America and China. Expanded research efforts will be needed to develop effective lure and trap systems for the multitude of invasive wood-boring beetles.
The inability of surveillance programs to detect the arrival of exotic wood borers such as A. glabripennis, T. fuscum, and A. planipennis demonstrates a need for alternative detection programs. While the use of trap systems that mimic host silhouettes and volatile profiles show some promise as detection tools for T. fuscum, the best attractant still appears to be host material. Indeed, the detection of both T. fuscum in Nova Scotia and Hylastes opacus (Erichson) in Oregon resulted from rearing of naturally attacked trees or the use of bait logs, respectively (Smith and Hurley 2000; Mudge et al. 2001). Rearing of bolts from dead and dying native trees has also been used effectively to detect invasive ambrosia beetles and determine their host ranges (Humble et al. 1998). While such evaluations provide definitive evidence of the presence of invasive species, the logistical effort required is resource intensive and thus limits the establishment of larger scale surveillance efforts.
Knowledge of the biology and ecology of newly discovered invasive species is critical to the development of risk assessments as well as to the development of detection, containment, or eradication strategies. Historically, the invasive arthropod fauna in North America has arrived from Europe. More recently, invasive species from Asia have predominated the incursions of bark and wood-boring beetles in North America. The radical increase in trade levels between China and North America, and the similarities of their physical environments and flora, suggest that China will remain a significant donor of invasive species (National Research Council 2002). These physical and floristic similarities, coupled with high levels of wood imports arising from the limited availability of forest resources in China (Wang et al. 2002), put China at risk as well.
In recognition of the risks posed to both regions, collaborative research projects have been established between the Canadian Forest Service and the Jilin Provincial Academy of Forest Sciences to evaluate the efficacy of lures used by Canadian quarantine surveillance programs against wood borers in the forests of northeastern China. And, projects are being initiated with the Chinese Academy of Sciences to study quarantine risks associated with invasive species.
Import inspections alone provide insufficient levels of protection against incursions of invasive species. Increased levels of international research collaboration are needed to address the economic and environmental issues related to the introduction of species via global trade. Fruitful areas of future surveillance research include:
Such efforts would best be enhanced through the development of stronger research linkages between national and international forest research organizations and National and Regional Plant Protection Organizations.
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1 Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, 506 West Burnside Road, Victoria, British Columbia, V8Z 1M5, Canada. [email protected]; Website: www.pfc.cfs.nrcan.gc.ca
2 S. Burke, Sales Manager, PheroTech Inc., Delta, British Columbia, Canada; personal communication, November 2002.